Exclusion-freeness in multi-party exchange protocols

In this paper we define a property for multi-party protocols called exclusion-freeness. In multi-party protocols respecting the strongest definition of this property, participants are sure that they will not be excluded from aproto col’s execution and, consequently, they do not have to trust each other any more. We study this property on a wellknown multi-party fair exchange protocol with an online trusted third party and we point out two attacks on this protocol breaking the fairness property and implying excluded participants. Finally, we propose a new multi-party fair exchange protocol with an online trusted third party respecting the strong exclusion-freeness property.5th International Conference on Information Security. Springer-Verlag. São Paulo, BrazilSCOPUS: cp.k